The invention relates to a floor covering. More particularly, the invention relates to a floor covering having an inorganic wear layer which preferably has been deposited on a support structure by a low pressure environment deposition technique. Further, the invention is directed to a multilayered floor covering in which each layer contributes to the wear performance and installation characteristics and affects the performance of the other layers.
Floor coverings having wear layers are well known in the art. Such wear layers protect the decorative layer of the floor coverings and lengthen the useful life of the floor covering. With the exception of ceramic tile which are rigid and must typically be installed on a mortar bed and metal floors such as steel plates, neither of which have a wear layer per se, inorganic material is not used as the wear surface of floor coverings. Inorganic materials are typically considered too brittle to be walked on; particularly if a "thin" layer were to be placed over a flexible or conformable support layer. Further, low pressure environment deposition techniques have not been applied to the manufacture of floor coverings.
Reduced pressure environment techniques for depositing films of hard inorganic materials include sputtering, plasma polymerization, physical vapor deposition, chemical vapor deposition, ion plating and ion implantation. Hard inorganic materials which can be prepared using these techniques include metals, metal oxides, metal nitrides and mixtures thereof; such as aluminum oxide, silicon oxide, tin and/or indium oxide, titanium dioxide, zirconium dioxide, tantalum oxide, chromium oxide, tungsten oxide, molybdenum oxide, aluminum nitride, boron nitride, silicon nitride, titanium nitride, and zirconium nitride, as well as metal halides, metal pnictides and metal chalogenides.
Often the partial pressures of key gases in the deposition environment are controlled to effect chemical reactions between depositing metal species. Therefore, a film formed on a substrate by reactive sputtering or reactive deposition can be a compound derived from a metal and a controlling gas, i.e., aluminum oxide produced by sputtering aluminum in oxygen. Sometimes the controlling gases are used to sustain a plasma in the deposition environment. Ion assisted deposition is a technique in which the controlled gas is ionized and is used to bombard the deposition surface to modify the morphology and physical properties of the resulting film.
A critical review of vapor deposition technology related to hard coatings was presented by J. E. Sundgren and H. T. C. Hentzell in J. Vac. Sci. Tech. A4(5), September/October 1987, 2259-2279. A more complete review of techniques involved in formation of thin films in reduced pressure environments is the book edited by J. L. Vossen and W. Kern, Thin Film Processes, Academic, New York, 1978.
Recent articles on thin film preparation include Yabinouitch, E., Gmitter, J. P., Haubison, J. P. and Bhat, R., Appl. Phys. Letter, 51(26), Dec. 28, 1987, 2222-2224 on etching Al/As to form free standing GaAlAs films; Clevenger, L. A., Thompson, C. V. and Cammarata, R. C., Appl. Phys. Letter, 52(10), Mar. 7, 1988, 795-797 on using commercial photoresists as supports; Ryszard Lamber, Thin Boehmite Films: Preparation and Structure; Journal of Materials Science Letters, 5(1986), 177-178; and Huling and Messing, J. Am. Ceram. Soc., 71(4), 1988, C222-C224, on coating on camphor and subliming to obtain free standing mullite.
Patents dealing with thin film deposition include: U.S. Pat. No. 4,604,181 and 4,702,963.
Reduced pressure environment techniques have been used to coat plastics materials such as plastic bags to improve gas impermeability. However, such coatings have been limited to about 0.5 microns in thickness.
While reduced pressure environment techniques have been used to form hard coatings on surfaces such as automobile parts, there has been no suggestion that such coatings could be successfully used as wear surfaces for floor coverings. In fact, such coatings tend to be brittle when applied in a substantial thickness. Thus, one skilled in the flooring art would not expect reduced pressure environment deposited materials to function adequately as a floor covering, particularly in the thickness deemed necessary to protect the decorative layer of a floor covering.
Alliance Wall manufactures and sells wall coverings in which porcelain enamel is fused to a steel sheet. However, use of a material as a wall covering does not suggest that it would be acceptable as a floor covering. Again, one skilled in the flooring art would not expect a thin sheet of ceramic to withstand the long term abuse to which flooring is subjected, particularly when laid over a resilient support structure and walked on by a woman in high heels.